CHANGE OF CHEMICAL AND BIOLOGICAL WATER ENVIRONMENT AT A NEWLY CONSTRUCTED RESERVOIR

The changes of chemical and biological water environment of Lake Sappo ro were investigated for over eight years from the beginning of water storage, and this is the first detailed report concerning the reservoi rs situated in sub-frigid zones in Japan, The pollution load flowing i nto this reservoir is only nature-derived. At Lake Sapporo, the large inflow of water from the melting snow in spring supplies the middle an d bottom layers with oxygen, and replaces water in the reservoir with new water. Under these circumstances, after effects of the initial det erioration were detected during two years in water quality, three year s in phytoplankton composition and four years in zooplankton compositi on. (C) 1998 IAWQ. Published by Elsevier Science Ltd.